It is the purpose of this project to determine: 1) if the concentrations of isoacceptor amino acyl-tRNAs in rabbit reticulocytes can modulate globin synthesis; 2) if modified isoacceptors (e.g., those in cancerous tissues) are decoded at the same rate as unmodified isoacceptors; and 3) which isoacceptors of Arg-, Gln-, Leu- and Ser-tRNAs code for which amino acid sites in rabbit globin (earlier studies have shown that each of these amino acyl-tRNAs contain isoacceptors in low levels in reticulocytes).